Coal vs. Natural Gas (And Just For Fun, Renewables)

U.S. government scientists are out with new data that shows that combined cycle gas plants emit 436 grams of CO2 per kilowatt hour of energy produced – less than half the 915 grams emitted by coal-based power plants.

An EarthTechling analysis concludes that this is 436 grams more than solar and wind power.

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Colbert Fossil Plant in Tuscumbia, Ala. (image via Tennessee Valley Authority)

The scientists, whose analysis was accepted for publication in the journal Earth’s Future [PDF], said in a press release that based on average annual U.S. household consumption of 11,280 kilowatt-hours of energy, relying strictly on coal power plants would yield 11.4 metric tons of CO2 emissions per household. But if all the power came from natural gas power plants using combined cycle technology – where gas turbines generate electricity, then waste heat is used to power a steam turbine – those CO2 emissions would plummet to 5.4 metric tons.

An EarthTechling analysis concludes that a household relying on solar and wind power would see its annual CO2 emissions fall to zero.

The scientists noted further benefits of combined cycle natural gas as a power generator over coal, saying “the switch from coal to natural gas has also contributed to reductions in emissions of NOx and SO2.” That’s because even though most coal plants emit significantly less of these two very unhealthy pollutants than they used to, gas is still far cleaner, with the average NOx emission intensity of a combined natural gas plant “7 percent of that of a coal power plant” and the SO2 emission intensity “0.2 percent of a coal power plant.”

An EarthTechling analysis concludes that wind and solar have NOx and SO2 emissions intensities of 0 percent of a coal power plant.

Of course, solar and wind aren’t dispatchable, although who knows, that might change. Also, there are emissions involved in building wind power and solar power that aren’t considered here, but that’s true for natural gas, too. As the scientists noted: “(T)he new analysis is limited to pollutants emitted during energy production and measured at stacks. The paper did not address levels of greenhouse gases and other pollutants that leak into the atmosphere during fuel extraction, for example.”

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.

  • PhilipKGlass

    The CO2 emissions of non-fossil electricity sources are not zero, but they are clearly in a much lower class. The median CO2 emission for solar PV is 46 grams per kilowatt hour; for utility scale wind it is 12 grams. IOW the renewables save 90% to 97% of the CO2 emissions relative to gas or 95% to 99% of the emissions relative to coal.

    Why aren’t solar and wind power CO2 impacts zero? It takes silicon, aluminum, glass, copper, steel, plastics, and concrete to build wind and solar installations. The production of these materials emits CO2 even though the facilities do not emit CO2 during operation.

    • Pete D

      Indeed — which is why I wrote, In the last paragraph of my piece, “there are emissions involved in building wind power and solar power that aren’t considered here.” I pointedly didn’t include those emissions in my analysis in order to do a fair comparison. After all, the figures for coal and natural gas emissions strictly counted only those “emitted during energy production” — that is, operation of the plant. For more about the life-cycle impacts of solar, see this earlier piece: